LED spots comprising multiple LED sources are widely used. Such LED spots, however, are bulky because each source requires an individual collimator. Since the area of the exit surface of the spot is limited, only a limited number of LED collimators will fit.
A possible solution would be to place the individual LED sources very close together and to use a single bigger collimator instead of individual collimators to fill the area of the exit surface more efficiently. This solution, however, is disadvantageous due to the thermal restrictions arising from the heat generation of the LED sources. Consequently, the LED sources need to be placed at some distance from each other for heat spreading reasons. This means that there need to be gaps between the LEDs whereby the area-averaged luminance of the total source is strongly reduced.
US 2008/0074752 A1 describes one attempt at providing a solution to the above mentioned problems in the form of employing an optical manifold such as to combine the light outputs of several LEDs into one common output. The use of an optical manifold, however, leads to very high losses of light as the light is guided from the input surfaces to the output surface of the optical manifold. US 2008/0074752 A1 attempts to solve this problem by providing the legs of the optical manifold leading from each input surface to the output surface as internal collimators and/or by providing square collimators at each input surface of the optical manifold. This solution, however, still exhibits high losses of light from the optical manifold. Furthermore, this solution still requires an individual collimator for each LED source, and therefore does not solve the above problems related to bulkiness. Furthermore, the requirement for an individual collimator for each LED source also leads to high production costs.
WO 2010/044030 discloses an illumination device comprising a light guide that is divided in separate regions, a light emitting device being arranged in each region. The different regions are separated by a partially transparent partition configured such that light with a given wavelength and incident on said partition is partly transmitted and partly reflected, therewith achieving a uniform illumination.
Thus, and further as there is in the market an ever increasing demand for high quality and high intensity light sources, there is still a need for a solution with which a minimum of light is lost as the light from several different LED light sources is combined. Furthermore, there is a need for a solution to the problem related to the bulkiness of the existing devices.